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| S9S08SG8E2MTJ Datasheet, PDF (125/320 Pages) Freescale Semiconductor, Inc – MC9S08SG8 MC9S08SG4 Data Sheet Addendum | |||
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Chapter 9 Analog-to-Digital Converter (S08ADCV1)
For temperature calculations, use the VTEMP25 and m values from the ADC Electricals table.
In application code, the user reads the temperature sensor channel, calculates VTEMP, and compares to
VTEMP25. If VTEMP is greater than VTEMP25, the cold slope value is applied in Equation 9-1. If VTEMP is
less than VTEMP25, the hot slope value is applied in Equation 9-1. To improve accuracy , calibrate the
bandgap voltage reference and temperature sensor.
Calibrating at 25ï°C will improve accuracy to ï± 4.5ï°C.
Calibration at 3 points, -40ï°C, 25ï°C, and 125ï°C will improve accuracy to ï± 2.5ï°C. Once calibration has
been completed, the user will need to calculate the slope for both hot and cold. In application code, the
user would then calculate the temperature using Equation 9-1 as detailed above and then determine if the
temperature is above or below 25ï°C. Once determined if the temperature is above or below 25ï°C, the user
can recalculate the temperature using the hot or cold slope value obtained during calibration.
Figure 9-1 shows the MC9S08SG8 block diagram with the ADC module highlighted.
MC9S08SG8 MCU Series Data Sheet, Rev. 7
Freescale Semiconductor
121
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